RESUMEN
OBJECTIVE: To review epidemiological data on thyroid cancer in Iran. METHODS: The Tehran Cancer Institute Data System Registry (TCIDSR) was used to identify patients with different histological types of thyroid cancer (TC) in Iran. Data were analysed from 438 thyroid cancer cases identified by the TCIDSR in 1998-99. Disease prevalence was calculated with reference to age, time and place. RESULTS: The TCIDSR recorded 438 primary malignancies of the thyroid gland: papillary, follicular, medullary, and anaplastic carcinomas accounted for 67.1%, 10.7%, 5.3% and 4.3% of cases, respectively. The remaining 12.6% were classified as OD (other diagnoses). The prevalence of TC was highest in ethnic Farsis. The age range of patients was 8-85 years. Mean patient age was 44.52+17.03 years (mean + SD) overall, 47.74+18.10 years in female patients and 43.04+16.34 years in male patients. Anaplastic (6.5% vs. 3.3%) and medullary (10.0% vs. 3.0%) cancers were more common in men than women. CONCLUSION: This study was undertaken to define the epidemiological aspects of thyroid carcinoma in Iran, an area of endemic iodine deficiency until fairly recently. Against expectation for an iodine-deficient area, the frequency distribution of tumours in our study was closer to that seen in iodine-rich areas. Additional research on the risk factors for thyroid cancer--genetic, ethnic, geographic and environmental--is needed to explain the high incidence of PTC overall, and among ethnic Farsis in particular, in Iran.